Express your answer as a mixed number simplified to lowest terms. $13\dfrac{5}{17}+8\dfrac{5}{17} = {?}$
Explanation: Separate the whole numbers from the fractional parts: $= {13} + {\dfrac{5}{17}} + {8} + {\dfrac{5}{17}}$ Bring the whole numbers together and the fractions together: $= {13} + {8} + {\dfrac{5}{17}} + {\dfrac{5}{17}}$ Add the whole numbers: $=21 + {\dfrac{5}{17}} + {\dfrac{5}{17}}$ Add the fractions: $= 21+\dfrac{10}{17}$ Combine the whole and fractional parts into a mixed number: $= 21\dfrac{10}{17}$